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Protecting The Amine Flash Drum
By Osmay Oharriz
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Vendor Team
BELZONA, INC.
Coatings
2000 NW 88th Court
Miami, FL 33172
Phone: (305) 594-4994
www.belzona.com
TESTEX
Quality control equipment
(302) 731-5693
www.testextape.com
TYVEK
Safety equipment
DuPont Building
1007 Market Street
Wilmington, DE 19898
(800) 441-7515
www.tyvek.com
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Yacimiento Sierra Chata is an oil and gas deposit located 93 miles (149.67km) southeast of the city of Neuquén, in the province of Neuquén, Argentina. It covers a total area of 864 km2 (86,400 ha) and contains 69 wells which produce 2,500,000 m3/D (3,269,877 yd3/D) of gas.
Yacimiento Sierra Chata Amine Sweetening Plant processes gas arising from Sierra Chata and from other gas deposits in the area. It is comprised of two production trains. As of April 2011, the plant processed 2,302 m3 of gas per day.
In 2006, the plant engineer at a workshop owned by Sica Metalurgica Argentina S.A, in the city of Esperanza, Province of Santa Fe, informed coating manufacturer, Belzona that the flash drum in the amine unit was suffering from internal general corrosion and the decision had been made to purchase a new drum and coat it with a Belzona product prior to putting it into service at its final destination, the Yacimiento Sierra Chata Amine Sweetening Plant.
Amine Sweetening Plants: Not A Sweet Process
Amine treatment plants are designed to remove acid gases such as carbon dioxide (CO2) and hydrogen sulfide (H2S) as well as mercaptans such as carbonyl sulfide (COS) and carbon sulfide (CS2) from natural gas and hydrocarbon process streams. CO2 can combine with water (H2O) creating carbonic acid (H2CO3), which although being weak, is very corrosive. Likewise, CO2 reduces the British Thermal Unit (BTU) value of gas, making it unmarketable if its concentration levels are found to be more than 3%. H2S is an extremely toxic gas which can also be verycorrosive to equipment
 Amine sweetening removes all these contaminants by means of reversible chemical reactions between the acid gas and the amine. This reaction leads to the formation of an amine-salt. The amines most commonly used are monoethanol amine (MEA), diethanol amine (DEA), diisopropanol amine (DIPA), methyl diethanol amine (MDEA), and diglycolamine (DGA). Amines themselves can be extremely aggressive and can also degrade chemically, resulting in simpler but sometimes more corrosive chemicals.
Amine sweetening plants are usually equipped with a liquid/gas treater, a flash drum, and a stripper or regenerator in addition to common equipment such as pumps and heat exchangers. In liquid/gas treaters, the feed gas or liquid comes in contact with the amine solution, absorbing the acid gas species in the process. The amine solution becomes enriched with acid gas--usually referred to as rich amine. The rich amine is then pumped to the flash drum which operates at a lower pressure to flash off soluble light hydrocarbons and aid in the removal of entrained or condensed hydrocarbons.
Corrosion in this unit is commonly attributed to the acid gases present in the treated streams which can readily attack the equipment, made in the majority out of carbon steel. Several corrosion measures are commonly taken in amine treatment plants. These range from designing the optimal combination of amine concentration, circulation rate, and acid gas loads to using protective organic coatings. In this case, the carbon steel equipment would have coated protection.
The carbon steel flash drum was 39.36' (11.10m) long and 9.48' (2.89m) in diameter. It would contain diglycolamine (DGA) amine held at an operating temperature of 176ºF (80°C) with a maximum temperature of 194ºF (90°C).
Coated Protection
 The coating material specified to be applied onto 1184.03 ft2 (109.10m2) of carbon steel internal wall was Belzona 1391 (Ceramic HT Metal). Belzona 1391 is a solvent-free, applicator- or brush-applied high temperature ceramic filled lining system, consisting of a base material mixed with a solidifier in base: solidifier proportions of 13:1 by weight and 5:1 by volume. It is used for elevated temperature applications requiring resistance to entrained solids and exposure to hydrocarbons and pressurized steam. It has excellent chemical resistance to a great variety of chemicals including amines, wet carbon dioxide and hydrogen sulfide, alkalis, and glycol. Belzona 1391 is applied as a one or a two-coat system at a minimum total DFT of 24 or 32 mil (0.61mm or 0.81mm) if exposed to immersion temperatures up to 212ºF or 250ºF (100°C or 121°C) respectively. It requires detergent washing and flash blasting between coats and can be inspected by wet sponge testing.
Work commenced on June 19th and concluded on June 21st. Total area of carbon steel coated was estimated to be 1,184.03 ft2 (109.10m2). All the surface preparation and coatings work was carried out by the incumbent contractor Hugo Garcia S.R.L and inspected by Furmanite Argentina S.A.
First, the surface was degreased and loose contamination was removed with industrial acetone. The surface was then abrasive blast cleaned to White Metal in accordance with NACE No. 1/SSPC-SP5 “White Metal Blast Cleaning” Standard. Next, the surface profile was measured to be 3 mil (0.10mm) in accordance with NACE RP028702 “Field Measurement of Surface Profile of Abrasive Blast-Cleaned Steel Surfaces using a Replica Tape” Standard.
Throughout the project, environmental parameters such as relative humidity, ambient temperature, and dew point were monitored.
Belzona 1391 (Ceramic HT Metal) was applied in a single coat system at 24-30 mil (0.61mm-0.76mm) DFT using brushes and applicators. The coating was visually inspected for pinholes and misses, and was allowed to cure as per coating manufacturer’s recommendation.
Inspection and Remedial Work
Once the coating had hardened as per the manufacturer’s recommendation, it was visually inspected for misses, pinholes, runs, sags, drips, voids and/or mechanical damage. Any defects found were marked and numbered for further identification and logging. Next, the substrate was washed with a warm detergent solution to remove any amine bloom that formed, rinsed with clean water, and left to dry.
Holiday inspection was conducted using a low-voltage wet sponge tester in accordance with NACE SP0188 “Discontinuity (holiday) Testing of New Protective Coatings on Conductive Substrates” Standard. Any holidays were marked and numbered for further remedial work—a light grit blast to a 1-2 mil (0.03mm-0.10mm) profile, degreasing, and repair with Belzona 1391.
Flash Drum Operation and Inspection
The flash drum was installed in 2008 during a shutdown. Later the same year, the plant decided to switch diglycolamine for methyl diethanol amine to improve CO2 removal. In 2010, the flash drum was opened for inspection. Belzona 1391 (Ceramic HT Metal) was found to be in perfect condition after being exposed to years of diglycolamine and methyl diethanol amine exposure.
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